Centrifugal pump



HEAD OF ELEMT/O/V Dec. 6, 1966 M. STEHRENBERGER ETAL 3,239,597

CENTRIFUGAL PUMP Filed Dec. 25, 1963 2 Sheets-Sheet 2 HEAD OF ELEVATIONA PUMP our/ ar Q 30% aur ur Q 1007,

FIG.3 FIGS BY wjamg W United States Pater 3,289,597 CENTRIFUGAL PUMP MaxStehreuberger, Brugg, Switzerland, and Leif Rasmussen, Glostrup,Denmark, assignors to K. Rutschi AG, Pumpenbau Brugg, Brugg, SwitzerlandFiled Dec. 23, 1963, Ser. No. 332,441 Claims priority,application/ivgitzerland, Jan. 16, 1963, 4 Claims. (Cl. 103-97) Actuallythe demand for centrifugal pumps, particularly in the central heatingfield where such pumps are used as circulators is such that the plumbersand the wholesalers keep stocks of them. Unfortunately, since thevarious types of central heating installations also require pumps ofvarying output, these dealers are obliged to have on stock severaldifferent types of pumps in order to be in a position to meet thedemand.

Of course the number of different types of pumps may be limited byconstructing the pumps for an output that covers the largest possiblerange of application. Smaller intermediate outputs may also be obtainedby cutting down on a lathe the pump impeller to a smaller diameter.However this last-mentioned step may be effected in a workshop only. Nowit may well occur that the pump output should be modified after themounting of the pump into the central heating installation, for exampleif it appears then only, that the pump output is too large or too small.The removal of the pump and its subsequent building-in in such a case istime-wasting and complicated so that it has been looked for a solutionpermitting adjustment of the pump output with the pump remaining mountedin the installation.

An adaption of a circulating pump to an existing central heatinginstallation would be possible by using gate valves, arrangedimmediately before and after the pump, to effect a throttling acting.But generally there is no possibility to fixedly adjust the conventionalgate valves in a desired position. Thus each time such a gate valve hasto be closed entirely in accordance with the prime object of suchvalves, be it for a checking of the central heating installation orbecause the installation is set out of operation, the subsequentreadjustment to the correct opening corresponding to the desired pumpoutput is rendered difiicult. Also in the case of such a' throttling bymeans of gate valves it is never exactly known which is the actual pumpoutput that is thereby obtained.

For all these reasons many attempts have been made to obtain differentoutput curves by means of simple devices provided at the pump itself, inorder to afford for subsequent regulation of the pump output when thepump is built-in on the one hand but also, on the other hand, in orderto make possible for the dealers to satisfy various requirements foroutput with the least possible number of different pump types.

For example it is known that the output measured at the pressure side ofthe pump may be influenced by a lateral displacement of the impellerleading to a partial backflow of the accelerated fluid, or by theprovision of a bypass through which the fluid is guided back from thepressure side to the suction side. This type of power regulation has theimportant drawback that the highest power consumption appears for thesmallest pump outputs so that pumps adjusted in this manner are veryuneconomical in operation.

The prime object of the present invention is to realize a circulatingpump with an incorporated power regulation, which does not present anyof the afore-mentioned drawbacks.

A further object of the invention is the realization of ice a powerregulation that leads to small power consumption when adjusted for smallpump output and to larger power consumption only when adjusted forhigher pump output.

These and other objects are obtained according to the present inventionby the provision of a throttling member mounted into the pump casing andadapted to regulate the amount of fluid flowing through the pump.

This throttling member may be mounted into the suction side of the pump,whereby the best constructional, mechanical and esthetical results areobtained.

However, if for any reasons, there is danger of formation of cavitationsthe throttling member may as well be built-in at the pressure side ofthe pump.

In both cases it is still a further object of the invention to realize astepless regulation of the pump output by the provision of a steplesslyadjustable throttling member.

A still further object of the invention is to facilitate the adjustmentof the desired pump power by means of the throttling member in suchmanner that the amount of fluid allowed to pass through the pump isvaried proportionally with the angle about which the throttling memberis rotated. This aim is achieved according to the invention by acorresponding form given to the gate wall of the throttling member thatprojects into the fluid current.

Other features and advantages of the invention will become apparent fromthe description now to follow, of preferred embodiments thereof, givenby way of example only, and in which reference will be made to thepartly diagrammatical accompanying drawings, in which:

FIGURE 1 is a section through a circulating pump having a throttlingmember incorporated into its suction side;

FIGURE 2 is a view of the outer parts serving to the adjustment of thepump output of the throttling member of FIGURE 1 as seen from left toright in the latter figure.

FIGURE 3 is a representation of output curves of the pump of FIGURE 1for different adjusting positions of the throttling member.

FIGURE 4 illustrates, diagrammatically, a known output regulation for acirculating pump by means of a bypass, and

FIGURE 5 illustrates output curves of the known arrangement of FIGURE 4for different adjustments.

Referring now to the drawings, in FIGURE 1 reference numeral 1designates a rotary throttling gate arranged in the suction opening 3 ofthe casing 4 of a centrifugal pump directly opposite the pump impeller5. The outline of the gate wall 2 is selected in such manner that when agate button 6, accessible from the outside of the pump, is turned, thatthen the fluid amount allowed to pass through the pump, i.e. the pumpdelivery, increases proportionally to the angle of rotation. For examplein the fully open position of the throttling member (position IV inFIGURE 2) the maximum amount of fluid shall be delivered, and in thehalf-closed position of the throttling member (position II in FIGURE 2)accordingly half of the maximum amount shall be allowed to pass throughthe pump. .Moreover the gate wall 2 may have such an outline as tocompletely close the suction tube 3 when the throttling member is closed(position 0 in FIGURE 2) or that when this position is adjusted by meansof the gate adjusting button 6, still a minimum amount of fluid isallowed to flow through the pump for security reasons. Thelast-mentioned eifect may of course also be obtained by means other thana particular outline shape of the gate wall.

At the passage of gate 1 through the pump casing 4 a sealing ring 7prevents leakage. According to FIGURE 2 the gate button 6 is providedwith a hand cooper- I ating with a scale on the pump casingindicatingthe positions of the button 6 when the pump output isregulated between ,1 and of the maximum output. A pair of lateralabutments 9 prevent turning of the button 6 beyond its regulating range.

Instead of being mounted centrally in the suction opening 3 as shown anddescribed hereinbefore the throttling member may also be mounted intothe pressure side tube of the pump designated by reference numeral 10.Such an arrangement is indicated in dot-and-dash lines in FIGURE 1. Itis to be understood that the described output regulation is not limitedfor use in connection with central heating circulators but may beincorporated analoguously into any other centrifugal pump. Neverthelessit is with central heating circulators that its widest possibilities ofuse and largest advantages appear.

FIGURE 3 illustrates the output regulation that may be obtained with theabove described arrangement of a throttling member. With the gate button6 in position IV the passage to the impeller in the suction opening 3 iscompletely free resulting in the maximum output shown by the outputcurve IV. In the positions III, II and I of the rotary gate button 6 thethrottling member is adjusted to throttle down more and more the passagefor the fluid, resulting in correspondingly reduced output curves.Thereby the power consumption of the pump is highest when the pump isregulated to full output and decreases with decreasing pump delivery inaccordance with the normal behavior of a radial centrifugal pumpimpeller. Thus with the described means for regulating the pump outputan economical ratio is obtained for all operation points, between theoutput and the power consumption.

In order to make appear the progress of this output regulation over thealready known solutions, one of the latter, namely the known outputregulation by means of backflow through a bypass conduit shall hereafterbe compared with the output regulation according to the invention.

FIGURE 4 diagrammatically shows a pump 12 in which the backflow, whichgenerally takes place within the pump through a boring from the pressureside into the suction side of the pump, is shown to flow through aseparate backflow bypass 13 for the sake of clarity.

Assuming now that a central heating installation is provided with astock pump having a maximum output of 100% of which, say, only 30% areactually required. The backflow valve 14, connected into the bypass 13may then be opened to such an extent, that 70% of the de livered fluidflows back from the pressure side to the suction side.

FIGURE illustrates the output curves obtained with such an outputregulation by means of backflow. With the bypass valve 14 closed, i.e.with no back flow at all, the obtained output curve IV corresponds tothe curve IV of FIGURE 3. As soon, however, as the valve 14 is openedand a certain amount of backflow established the obtained curves III, IIand I difler from the curves of FIGURE 3 corresponding to the same pumpoutput. If, for a determined conduit resistance of a central heatinginstallation or owing to a small required head of elevation H only, say,30% of the maximum pump output are required the power consumption willbe, as clearly shown, the same as for the full output of 100% of thepump. With this output regulation by backflow the contradictory aspectoccurs, that for the maximum output of the pump thepower consumptioncurve is the lowest while for the smallest output, according to theoutput curve I, the power consumption is the highest.

This clearly demonstrates the technical progress obtained with theoutput regulation according to the present inventiOH, whereby, inaddition, the obtained output curves as represented in FIGURE 3 haveparticular advantages in connection with the operation of circulatorsfor central heating installations. With the arrangement according to theinvention it is possible to determine very easily the required output ofa circulating pump, since the required heating output in ratio to thedesired temperature difference indicates the necessary output. The headof elevation of a pump is substantially more diflicult tocalculate'since the conduits lengths and the number and type of castingsstrongly influence the calculation.

With the output regulation according tothe present invention a preciseprior calculation of the conduit re sistance and of the head ofelevation is of minor importance since the fluid output, which isimportant for the temperature difference remains'practically the sameover a wide range independently of the head of elevation.

We claim:

1. A circulating pump comprising a pumpcasing defining an impellerchamber, a transverse inlet passage leading to said impeller chamber andincluding an inlet chamber adjacent to and coaxial with said impellerchamber and a discharge passage leading away from said impeller chamber,an impeller rotatably mounted in said impeller chamber, means connectedto said impeller to rotate said impeller, a throttle member mounted insaid inlet chamber and being rotatable to vary the flow area throughsaid inlet passage, said throttle member comprising a gate including awall portion which may be moved across the inlet passage to block atleast a portion of the flow therethrough, and adjusting means on theexterior of said casing connected to said throttle member to rotate saidthrottle member to vary the amount of fluid circulated through saidinlet passage to said impeller.

2. A circulating pump comprising a pump casing defining an impellerchamber, a transverse inlet passage leading to said impeller chamber andincluding an inlet chamber adjacent to and coaxial with said impellerchamber and a discharge passage leading away from said impeller chamber,an impeller rotatably mounted in said impeller chamber, a throttlemember mounted in said inlet chamber and being rotatable to vary theflow area through said inlet passage, said throttle member comprising agate including a wall portion which may be moved across the inletpassage to block at least a portion of the flow therethrough, adjustingmeans on the exterior of said casing connected to said throttle memberto rotate said throttle member to vary the amount of fluid flow throughsaid inlet passage to said impeller, and a motor connected to saidimpeller to rotate said impeller arranged on the side of said impelleropposite to said throttle member.

3. A circulating pump comprising a pump casing defining an impellerchamber, a transverse inlet passage leading to said impeller chamber andincluding an inlet chamber adjacent to and coaxial with said impellerchamber and a discharge passage leading away from said impeller chamber,an impeller rotatably mounted in said impeller chamber, means connectedto said impeller to rotate said impeller, a throttle member mounted insaid inlet chamber and being rotatable to vary the flow area throughsaid inlet passage, said throttle member comprising a gate including awall portion which may be moved across the inlet passage to block atleast a portion of the flow therethrough, and a rotatable member mountedon the exterior of said casing and connected to said throttle member torotate said throttle member in proportion to the rotation of saidrotatable member to vary the flow area through said inlet passage.

4. A circulating pump comprising a pump casing defining an impellerchamber, a transverse inlet passage leading to said impeller chamber andincluding an inlet chamber adjacent to and coaxial with said impellerchamber and a discharge passage leading away from said impeller chamber,an impeller rotatably mounted in said impeller chamber, means connectedto said impeller to rotate said impeller, a throttle member mounted insaid inlet chamber and being rotatable to vary the flow area throughsaid inlet passage, said throttle member comprising a gate including aWall portion which may be moved across the inlet passage to block atleast a portion of the flow therethrough, and a rotatable member mountedon the exterior of said casing and connected to said throttle member torotate said throttle member in proportion to the rotation of saidrotatable member to vary the flow area through said inlet passage, saidrotary member comprising a knob having an index point, and scale meansdefined on said casing adjacent said knob for indicating the adjustmentof said throttle member.

References Cited by the Examiner UNITED STATES PATENTS 5/1909 Trent103-97 3/1917 Doble 10397 8/1923 Sherzer 103-97 12/1943 Gregory 230--1147/1964 Tyler 103--97 FOREIGN PATENTS 1/ 1909 Great Britain. 10/1913Great Britain.

9/ 1940 Sweden.

15 LAURENCE V. EFNER, Primary Examiner.

1. A CIRCULATING PUMP COMPRISING A PUMP CASING DEFINING AN IMPELLERCHAMBER, A TRANSVERSE INLET PASSAGE LEADING TO SAID IMPELLER CHAMBER ANDINCLUDING AN INLET CHAMBER ADJACENT TO AND COAXIAL WITH SAID IMPELLERCHAMBER AND A DISCHARGE PASSAGE LEADING AWAY FROM SAID IMPELLER CHAMBER,AN IMPELLER ROTATABLY MOUNTED IN SAID IMPELLER CHAMBER, MEANS CONNECTEDTO SAID IMPELLER TO ROTATE SAID IMPELLER, A THROTTLE MEMBER MOUNTED INSAID INLET CHAMBER AND BEING ROTATABLE TO VARY THE FLOW AREA THROUGHSAID INLET PASSAGE, SAID THROTTLE MEMBER COMPRISING A GATE INCLUDING AWALL PORTION WHICH MAY BE MOVED ACROSS THE INLET PASSAGE TO BLOCK ATLEAST A PORTION OF THE FLOW THERETHROUGH, AND ADJUSTING MEANS ON THEEXTERIOR OF SAID CASING CONNECTED TO SAID THROTTLE MEMBER TO ROTATE SAIDTHROTTLE MEMBER TO VARY THE AMOUNT OF FLUID CIRCULATED THROUGH SAIDINLET PASSAGE TO SAID IMPELLER.